Animals must time demanding events such as reproduction so as to coincide with favorable environmental conditions. In some cases, environmental conditions change on regular seasonal schedules, and in others they change more capriciously. In this talk I will discuss how birds coping with different degrees of environmental unpredictability have evolved to use environmental cues such as photoperiod to regulate their annual schedules of reproduction, plumage replacement and migration. A comparative approach reveals that seasonal breeders and opportunists - typically thought to represent opposite extremes on a "temporal flexibility continuum" - do in fact possess environmental cue response features that represent adaptations to the different degrees of environmental predictability that they face. However it is also evident that these species share some surprising commonalities that may reflect constraints on temporal flexibility imposed by a trade-off between maximizing current versus future reproductive opportunities.

Evolution of environmental cue response systems in birds:

Adaptive specializations or variations on a theme of white-crowned sparrow?